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------------------------------------------------------------------------------
-- --
-- --
-- ASIS UTILITY LIBRARY COMPONENTS --
-- --
-- A S I S _ U L . S I M P L E _ S T A C K S --
-- --
-- S p e c --
-- --
-- Copyright (C) 2012-2014, AdaCore --
-- --
-- Asis Utility Library (ASIS UL) is free software; you can redistribute it --
-- and/or modify it under terms of the GNU General Public License as --
-- published by the Free Software Foundation; either version 3, or (at your --
-- option) any later version. ASIS UL is distributed in the hope that it --
-- will be useful, but WITHOUT ANY WARRANTY; without even the implied --
-- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the --
-- GNU General Public License for more details. You should have received a --
-- copy of the GNU General Public License distributed with GNAT; see file --
-- COPYING3. If not, go to http://www.gnu.org/licenses for a complete copy --
-- of the license. --
-- --
-- ASIS UL is maintained by AdaCore (http://www.adacore.com). --
-- --
------------------------------------------------------------------------------
pragma Ada_2012;
-- Defines a simple unlimited stack abstraction.
with Ada.Containers.Vectors;
generic
type Element_Type is private;
No_Element : Element_Type;
with function "=" (Left, Right : Element_Type) return Boolean is <>;
package ASIS_UL.Simple_Stacks is
-- Element_Type is the type of the stack elements.
--
-- No_Element is the special value to be returned in case if the state of
-- the stack does not allow the given operation to return any meaningful
-- result. That is, opposite to the classical stac abstraction, this one
-- returns No_Element instead of raising an exception.
--
-- The main usage of this stack is to be used as a state of
-- Traverse_Element - if we Push an element being visited in Pre_Operation
-- and Pop it in Post_Operation, then the stack gives us the track to the
-- top of our traversal (No_Element is set to Nil_Element).
type Simple_Stack is private;
procedure Push (S : in out Simple_Stack; Elem : Element_Type);
-- Places Elem on the top of the stack
function Pop (S : in out Simple_Stack) return Element_Type;
-- Returns the top element of the stack and removes this element from
-- the stack. Returns No_Element if the stack is empty
procedure Pop (S : in out Simple_Stack);
-- Removes the top element from the stack. Does nothing if the stack
-- is empty
function Top
(S : in out Simple_Stack;
Step_Down : Natural := 0)
return Element_Type;
-- Returns the top element of the stack without removing this element from
-- the stack. Returns No_Element if the stack is empty. If Step_Down is
-- not 0, returns the Element which is Step_Down steps to the bottom of the
-- stack, except if the stack depth is less than Step_Down, otherwise
-- No_Element is returned
function Size (S : in out Simple_Stack) return Natural;
-- Returns the number of elements in the stack
function Is_Empty_Stack (S : in out Simple_Stack) return Boolean;
-- Same as Size = 0
private
package Simple_Stacks_Package is new Ada.Containers.Vectors
(Index_Type => Natural,
Element_Type => Element_Type,
"=" => "=");
type Simple_Stack is new Simple_Stacks_Package.Vector with null record;
end ASIS_UL.Simple_Stacks;
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